Modern thermal underwear is a type of underclothing with flat slip stitches used as the first warming layer in protection against low temperatures. It is made of a special knitted fabric consisting of synthetic or combined (synthetic and natural) threads.
For the purpose intended there are two types of thermal underwear.
- Moisture-diverting (for high physical activity)
Insulating thermal underwear
Insulating thermal underwear (key function: warmth-keeping) — feature knitted goods made of one-layer (WOOLPER thermal underwear) or two-layer material (MONBLAN thermal underwear) including natural wool (55–70%).
The inner material in two-layer thermal underwear is made of soft and smooth, and body-pleasing polyether threads. The outer layer comprising natural wool threads doest not touch the skin surface and is non-irritating.
The main principle of thermal underwear comprising wool is that non-insulating air contained between the outer layer wool fibers keeps body warmth inside and prevents skin contact with the outside cold air. Besides, the wool «breathes», absorbs body evaporated moisture, makes warm even if it is wet. Two-layer thermal underwear can be used kept on for a long time (8 hours).
Thermal underwear for high physical activity
Thermal underwear for high physical activity (key function: body-evaporated moisture divert) — knitted goods made of threads with special synthetic fibers structue (polyamide — 55%, polyether — 40%, elastane — 5%).
This thermal underwear knit has a mesh structure. Meshes fitting to body divert moisture, and the upper layer meshes distribute it on the material surface and rapidly evaporate it.
Meshes also function as «pockets», containing warm air. Contacting with body, the air in fibers is warmed up to a comfort temperature creating a protective insert. This insert between skin and ambient cold environment pushes moisture out of thermal underwear due to pressure difference. This reduces body heat loss in cold weather, adds a sense of comfort and protects body from overcooling and overheating.
How to use thermal underwear for high physical activity?
You must put thermal underwear directly on body and use only during physical activity.
Thermal underwear must necessarily fit to body, otherwise it will not perform its function. Therefore, you must choose thermal underwear exactly to size or a smaller size.
When sweat released during physical activity, accumulates in a regular underwear material it reduces its insulating properties. Water heat transmission is 25 times higher than that of air, so in wet clothing you will get cold 25 times faster than in dry one!